This invention relates generally to electrical connecting devices for terminating cords of the modular plug type currently being utilized in the telephone industry for terminating cords extending between the base and handset of a telephone as well as between the base and a wall terminal block. More particularly, the invention relates to modular connectors of the above type wherein such connectors are provided with means for more positively securing the terminal ends of a cord to the electrical connector than was heretofore possible.
Modular plug type connectors are finding increasing use in the telephone industry in connection with terminating cords extending between the base and handset of a telephone as well as between the telephone base and the wall mounted terminal block. Generally, such connectors are used to terminate so-called "flat" cords having a multiplicity of insulated conductors arranged in a spaced linear array within an outer jacket. Various configurations of such connectors are disclosed in various patents assigned to Western Electric Company, Inc., such for example as U.S. Pat. No. 3,699,498 issued Oct. 17, 1972; 3,761,869 issued Sept. 25, 1973; 3,860,316 issued Jan. 14, 1975; and 3,954,320 issued May 4, 1976. Although such connectors have been made from two housing components bonded together (see, e.g., U.S. Pat. No. 3,761,869), it appears preferable to manufacture such connectors utilizing a so-called unipartite or integrally molded housing (see, e.g., U.S. Pat. No. 3,998,514).
In the case of connectors having housings of the unipartite type, such housings generally define an internal cord receiving cavity into which the end of a cord is inserted through a cord receiving aperture formed at one of the housing ends. The cord receiving cavity includes a jacket receiving portion adjacent the aperture and a communicating conductor receiving portion into which the individual insulated conductors, from which the outer jacket has been stripped, are received. A plurality of flat contact terminals, corresponding in number to the number of conductors of the cord, are inserted into individual grooves defined in the housing, each terminal being aligned with and electrically engaging a respective conductor. The conductors are generally of the tinsel type while the terminals have blade-like portions which engage respective conductors in a solderless connection. The flat terminals have edges which are exposed externally of the housing for engagement with respective aligned contact elements provided in the jack or the handset.
In connection with the unipartite connector housings described above, it has been conventional to provide means integral with the housings for positively securing the cord end to the connector so as to prevent separation of the connector from the cord during customer use as well as for providing strain-relief facilities for the conductors and jacket. Thus, as described in U.S. Pat. No. 3,860,316, strain relief and locking facilities for both the jacket and the conductors are provided integrally with the unipartite housing. More particularly, as described in the aforementioned patent, a first strain relief and locking means is provided which comprises an anchoring member provided within an opening formed in the housing which communicates with the jacket receiving portion of the cord receiving cavity. This jacket anchoring member is connected to the housing along one edge thereof by a transversely extending plastic hinge and along an opposed edge by a thin web of dielectric material. A second strain-relief and locking means is provided for the conductors which comprises a conductor-anchoring member which spans an opening which is aligned over the conductor receiving portion of the cord receiving cavity, the conductor-anchoring member being integrally formed with the opening walls through connecting portions. After appropriately locating the conductor and jacket portions of the cord end in the respective conductor and jacket receiving portions of the cord receiving cavity, the jacket and conductor-anchoring members are subjected to inward forces through the application of suitable tools whereby the web of the jacket anchoring member is sheared so that the latter pivots about the plastic hinge until a relatively planar surface thereof engages the jacket. Similarly, the conductor-anchoring member is sheared along irregular planes until its inner, relatively planar surface engages the conductors. In this manner, the connector is affixed to the cord and strain-relief is provided for the jacket and the conductors.
It has been found, however, that in fact, the degree of affixation of the cord to the connector afforded by the conventional jacket and conductor anchoring members, described above, is not entirely satisfactory. Thus, while the conventional construction described above has been found adequate for most normal usage of associated telephone equipment, cord-connector separation has been experienced when the associated telephone equipment has been subjected to a more rigorous usage. Thus, it is not uncommon for the cord to separate from the connector when the telephone instrument is tugged upon by children in a playful manner. In such cases, the cord will separate either intact from the connector, or alternatively, the conductors will be torn as the jacketed portion of the cord is pulled up from the connector thereby leaving short ends of the torn conductors within the cord cavity. In the latter case, the conductor-anchoring member tends to act as a knife-edge on the conductors thereby promoting failure in this manner. In either case, such cord-connector separation is quite inconvenient and necessarily requires a replacement of the entire cord-connector assembly.